246 research outputs found
Parsing demographic effects of canine parvovirus on a Minnesota wolf population
We examined 35 years of relationships among wolf (Canis lupus) pup survival, population change and canine parvovirus (CPV) seroprevalence in northeastern Minnesota to determine when CPV exerted its strongest effects. Using correlation analysis of data from five periods of 7-years each from 1973 through 2007, we learned that the strongest effect of CPV on pup survival (r = -0.73) and on wolf population change (r = -0.92) was during 1987 to 1993. After that, little effect was documented despite a mean CPV seroprevalence from 1994 of 2007 of 70.8% compared with 52.6% during 1987 to 1993. We conclude that after CPV became endemic and produced its peak effect on the study population, that population developed enough immunity to withstand the disease
Improved characterisation of intra-night optical variability of prominent AGN classes
The incidence of intra-night optical variability (INOV) is known to to differ
significantly among different classes of powerful active galactic nuclei (AGN).
A number of statistical methods have been employed in the literature for
testing the presence of INOV in the light curves, sometimes leading to
discordant results. In this paper we compare the INOV characteristics of six
prominent classes of AGN, as evaluated using three commonly used statistical
tests, namely the test, the modified test and the test, which
has recently begun to gain popularity. The AGN classes considered are:
radio-quiet quasars (RQQs), radio-intermediate quasars (RIQs), lobe-dominated
quasars (LDQs), low optical polarization core-dominated quasars (LPCDQs), high
optical polarization core-dominated quasars (HPCDQs), and TeV blazars. Our
analysis is based on a large body of AGN monitoring data, involving 262
sessions of intra-night monitoring of a total 77 AGN, using 1-2 metre class
optical telescopes located in India. In order to compare the usefulness of the
statistical tests, we have also subjected them to a `sanity check' by comparing
the number of false positives yielded by each test with the corresponding
statistical prediction. The present analysis is intended to serve as a
benchmark for future INOV studies of AGN of different classes.Comment: 26 pages, 2 tables, Accepted for publication in MNRA
Further evidence for intra-night optical variability of radio-quiet quasars
Although well established for BL Lac objects and radio-loud quasars, the
occurrence of intra-night optical variability (INOV) in radio-quiet quasars is
still debated, primarily since only a handful of INOV events with good
statistical significance, albeit small amplitude, have been reported so far.
This has motivated us to continue intra-night optical monitoring of bona-fide
radio-quiet quasars (RQQs). Here we present the results for a sample of 11 RQQs
monitored by us on 19 nights. On 5 of these nights a given RQQ was monitored
simultaneously from two well separated observatories. In all, two clear cases
and two probable case of INOV were detected. From these data, we estimate an
INOV duty cycle of 8% for RQQs which would increase to 19% if the
`probable variable' cases are also included. Such comparatively small INOV duty
cycles for RQQs, together with the small INOV amplitudes (1%), are in
accord with the previously deduced characteristics of this phenomenon.Comment: 15 Pages, 4 Tables, 24 Figures; Accepted in BAS
On the photometric error calibration for the `differential light curves' of point-like Active Galactic Nuclei
It is important to quantify the underestimation of rms photometric errors
returned by the commonly used \emph APPHOT algorithm in the \emph IRAF
software, in the context of differential photometry of point-like AGN, because
of the crucial role it plays in evaluating their variability properties.
Published values of the underestimation factor, , using several different
telescopes, lie in the range 1.3 - 1.75. The present study aims to revisit this
question by employing an exceptionally large data set of 262 differential light
curves (DLCs) derived from 262 pairs of non-varying stars monitored under our
ARIES AGN monitoring program for characterizing the intra-night optical
variability (INOV) of prominent AGN classes. The bulk of these data were taken
with the 1-m Sampurnanad Telescope (ST). We find = 1.540.05 which
is close to our recently reported value of = 1.5. Moreover, this
consistency holds at least up to a brightness mismatch of 1.5 mag between the
paired stars. From this we infer that a magnitude difference of at least up to
1.5 mag between a point-like AGN and comparison star(s) monitored
simultaneously is within the same CCD chip acceptable, as it should not lead to
spurious claims of INOV.Comment: 20 pages, 3 figures and 1 table; accepted for publication in JAp
Survival of porcine reproductive and respiratory syndrome virus in fresh pork
Porcine reproductive and respiratory syndrome virus (PRRSV) remains one of the most economically important diseases of pigs. Transmission of PRRS virus has been reported through many routes, with aerosol route being the most predominant. There may also be a potential risk of transmission through contami-nated pork, but this has never been investigated. The purpose of this study was to experimentally contaminate fresh pork with three different concentrations of PRRSV and to study virus survival at ambient (25 °C), refrigerated (4 °C), and frozen (−20 °C) temperatures. Concentrations of virus representing natural infectivity level and ‘worst case scenario’ were studied. The virus was detected in fresh pork at all three virus concentrations for up to 48 h at ambient temperature. At 4 °C, the virus survived for 6 days in pork inoculated with the higher virus concentration and for 3 days in pork inoculated at the lower concentration. At frozen temperature, PRRSV was detected for up to 60 days in pork inoculated at the higher concentration and for 7 days in pork inoculated at the lower concentration. These results suggest that fresh pork has the potential to be a vehicle for virus dissemination depending upon temperature and time of storage
Viruses and Drug Resistant Bacteria in Groundwater of Southeastern Minnesota
ABSTRACT-Karst topography of soils in southeastern Minnesota is responsible for the formation of sinkholes, subsurface cracks, and underground rivers which may enhance the transportation of surface contaminants into groundwater. The present study was conducted to determine the presence of human pathogenic viruses, coliforms, fecal coliforms and coliphages in private rural wells of this area. The occurrence of drug resistance in bacteria isolated from groundwater also was studied. Coliform bacteria were detected at least once from 22 of the 26 sites sampled over 34 months. Water from 10 sites yielded drug-resistant indicator bacteria; 25 of 38 (65.8 percent) total coliforms and 9 of27 (33.3 percent) fecal coliforms tested were found to carry drug resistance. Human enteric viruses were detected by DNA hybridization and/or virus isolation techniques in nine samples from seven different sites, some in the absence of fecal coliforms. Of the 161 samples tested for coliphages, 13 samples from seven sites were found positive. On two occasions, coliphages were isolated from samples in which coliforms were absent. These findings indicate that potential public health problems exist in this region
CASPR: Customer Activity Sequence-based Prediction and Representation
Tasks critical to enterprise profitability, such as customer churn
prediction, fraudulent account detection or customer lifetime value estimation,
are often tackled by models trained on features engineered from customer data
in tabular format. Application-specific feature engineering adds development,
operationalization and maintenance costs over time. Recent advances in
representation learning present an opportunity to simplify and generalize
feature engineering across applications. When applying these advancements to
tabular data researchers deal with data heterogeneity, variations in customer
engagement history or the sheer volume of enterprise datasets. In this paper,
we propose a novel approach to encode tabular data containing customer
transactions, purchase history and other interactions into a generic
representation of a customer's association with the business. We then evaluate
these embeddings as features to train multiple models spanning a variety of
applications. CASPR, Customer Activity Sequence-based Prediction and
Representation, applies Transformer architecture to encode activity sequences
to improve model performance and avoid bespoke feature engineering across
applications. Our experiments at scale validate CASPR for both small and large
enterprise applications.Comment: Presented at the Table Representation Learning Workshop, NeurIPS
2022, New Orleans. Authors listed in random orde
DEMOGRAPHIC EFFECTS OF CANINE PARVOVIRUS ON A FREE-RANGING WOLF POPULATION OVER 30 YEARS
We followed the course of canine parvovirus (CPV) antibody prevalence in a subpopulation of wolves (Canis lupus) in northeastern Minnesota from 1973, when antibodies were first detected, through 2004. Annual early pup survival was reduced by 70%, and wolf population change was related to CPV antibody prevalence. In the greater Minnesota population of 3,000 wolves, pup survival was reduced by 40–60%. This reduction limited the Minnesota wolf population rate of increase to about 4% per year compared with increases of 16–58% in other populations. Because it is young wolves that disperse, reduced pup survival may have caused reduced dispersal and reduced recolonization of new range in Minnesota
Use of Real-time PCR to Detect Canine Parvovirus in Feces of Free-ranging Wolves
Using real-time PCR, we tested 15 wolf (Canis lupus) feces from the Superior National Forest (SNF), Minnesota, USA, and 191 from Yellowstone National Park (YNP), USA, collected during summer and 13 during winter for canine parvovirus (CPV)-2 DNA. We also tested 20 dog feces for CPV-2 DNA. The PCR assay was 100%sensitive and specific with a minimum detection threshold of 104 50% tissue culture infective dose. Virus was detected in two winter specimens but none of the summer specimens. We suggest applying the technique more broadly especially with winter feces
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